Ultra-low NA step-index large mode area Yb-doped fiber with a germanium doped cladding for high power pulse amplification.

High concentration rare earth doped, large mode area (LMA) step-index fibers, which feature a very high cladding absorption per unit length at the pump wavelength, high efficiency, and excellent beam quality, are ideal for high power pulsed fiber lasers/amplifiers where large effective mode areas and short device lengths are crucial in order to reduce detrimental nonlinear effects associated with high peak power operation. In this Letter, we realize low numerical aperture (NA) high absorption fibers, simply by employing a germanium (Ge)-doped cladding rather than a pure silica cladding to offset the high refractive index associated with using a high concentration of ytterbium (Yb) in the core. This approach allows us to separate the two inter-linked fiber design parameters of pump absorption and NA in a step-index fiber. Using a conventional modified chemical vapor deposition process combined with solution doping, a low NA (0.04), LMA (475µm2) silica fiber is fabricated with a cladding absorption value of >20dB/m, which is the highest value among LMA step-index fibers with NA<0.06 so far reported to the best of our knowledge. The fabricated Yb-doped fiber was tested in a high-power picosecond amplifier system and enabled the generation of 190 ps laser pulses with a 101 µJ pulse energy and 0.5 MW peak power at an average power of 150 W.

AIDS-related knowledge among adult males in Chongqing City / 中华男科学杂志

<p><b>OBJECTIVE</b>To evaluate AIDS-related knowledge among adult men in Chongqing City, and provide some evidence for AIDS-related health education.</p><p><b>METHODS</b>Using the randomized multistage stratified cluster sampling method, we investigated AIDS-related knowledge among the adult males in Chongqing City.</p><p><b>RESULTS</b>Of the 1502 adult men, those who knew the three major transmitting routes of AIDS (blood-borne, vertical transmission and sexual contact) constituted 85.35, 83.16 and 66.11%, respectively, and 22.70% did not know the proper use of condoms. Those who thought that AIDS could be transmitted by mosquito bite, kissing, dining together, handshake or embracing made up 54.86, 50.6, 30.29 and 19.11%, respectively. The floating population scored significantly lower than the resident population in total AIDS knowledge, HIV transmission knowledge and HIV non-transmission knowledge (P<0.01).</p><p><b>CONCLUSION</b>AIDS-related knowledge among the adult men in Chongqing City needs to be improved by enhancing targeted AIDS-related health education.</p>

An assistant artificial hip joint / 中国医疗器械杂志

The assistant artificial hip joint (AAHJ) is a new impermanent hip support implanted in the body. It is used for treatment of ischemic necrosis of the femoral head at the early stage. It reserves the natural femoral head, increases its containment and decreases its load, thus makes the recovery of the necrosed femoral head. The AAHJ's moving axis center is the same as that of the femoral head. Therefore, the moving range of the hip joint is very close to the normal postoperatively. The patient can walk with loading in 3 weeks after the surgical operation, and can regain his (or her) daily work and life in 2 to 3 months of the operation. The AAHJ's structure is simple and the price is cheap.